Process for lubricating leather

ABSTRACT

Leather is lubricated by impregnating it with an aqueous emulsion made by mixing ASA or ASA and other oils with a watersoluble, polar organic compound. The oils are completely incorporated into the leather from the emulsion while the watersoluble, polar organic compound remains in the float. A non-exclusive irrevocable royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

United States Patent Luvisi et al.

PROCESS FOR LUBRICATING LEATHER Inventors: Fred P. Luvisi, Elkins Park; Edward M. Filachione; William J. Hopkins, both of Philadelphia, all of Pa.

Assignee: The United States of America as represented by the Secretary of Agriculture, Washington, DC.

Filed: Jan. 5, 1971 Appl. No.: 104,172

Related US. Application Data Division of Ser. No. 880,432, Nov. 26, 1969, abandoned, which is a continuation-inpart of Ser. No. 482,634, Aug. 25, 1965, abandoned.

US. Cl. 8/94.23, 117/142, 252/857 Int. Cl. Cl4c 9/02 Field of Search 8/9422, 94.23;

References Cited UNITED STATES PATENTS 12/1966 Neher et al. 8/9422 Primary Examiner-Leon D. Rosdol Assistant Examiner-Harold Wolman AttorneyRubin Hoffman [57] ABSTRACT Leather is lubricated by impregnating it with an aqueous emulsion made by mixing ASA or ASA and other oils with a water-soluble, polar organic compound. The oils are completely incorporated into the leather from theemulsion while the water-soluble, polar organic compound remains in the float.

A non-exclusive irrevocable royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

7 Claims, No Drawings PROCESS FOR LUBRICATING LEATHER This invention is a division of Ser. No. 880,432, filed Nov. 26, 1969, and now abandoned; the aforesaid abandoned application is a continuation-in-part of application Ser. No. 482,639, filed Aug. 25, 1965, and now abandoned.

This invention relates to lubrication of leather. More particularly, this invention relates to a new process for lubricating leather with water-insolbule, oil-soluble polar substances such as alkylated or alkenylated succinic acids or anhydrides, hereinafter referred to as ASA, of the type R-CHCO H where-B? is. alkyl or alkenyl ofll more QFDQD atoms. The alkenyl succinic acids and/or anhydrides are available by interaction of a long chain a-oletin with maleic anhydride or maleic acid. Hydrogenation of these materials produces the alkyl succinic acids and/or anhydrides. In actual commerce pure a-olefins may not be used, hence mixtures are often produced with a preponderance of a particular chain length. In our invention reaction products where R is alkyl or alkenyl of twelve or more carbon atoms have been found operative. However, in our invention we prefer alkenyl or alkyl succinic acids in which R contains on the average 18 carbon atoms.

An object of the present invention is to provide a process for lubricating leather with very small amounts of lubricant.

Another object is to'provide a process for lubrication of leather that can be carried out in conventional equipment and by conventional processes commonly used in fat-liquoring of leather.

A further object of this invention is to describe a practical and inexpensive process for lubrication of leather with an alkyl or alkenyl substituted succinic acid, or derivative thereof. I

Another object of the invention is to provide a process for lubricating leather so that on drying a soft, mellow leather results without the need for a staking operation.

Another object of the invention is to provide a process for lubricating leather so that the leather lends itself to efficient water repellent processes.

A further object of this invention is to provide a process for lubricating mineral tanned leather or leather tanned with a combination of a mineral tanning agent and an organic tanning agent such as vegetable tans, aldehydes, syntans, resins, etc., with an alkyl or alkenyl succinic acid. 7

When unlubricated wet leather, such as chrome leather in the blue,-is allowed to become dry it becomes hard and stiff and difficult to process further. For this reason chrome leather is not dried or brought to the crust stage until after it is lubricated. In the crust chrome leather is stiff, but it can be readily hydrated for further processing, one such process being staking. In commercial practice lubrication is by means of fat liquors which contain one or more animal and/or vegetable oils together with one or more surface active agents. The process is usually conducted-by drumming the tanned stock with the fat liquor, which is an oil-inwater type emulsion at an elevated temperature, generally 45-5 C., for about a half hour. Usually the lubricant is exhausted from the treating bath and enters the leather fibers. This general procedure has been used by the leather tanners for many years.

Recently, G. H. von Fuchs (British Pat. No. 925,174zJALCA, 52, 550-559, Oct, 1957) proposed a novel method for lubricating leather. This method comprised wringing the chrome-tanned leather to reduce the moisture content to between 45 percent and 60 percent and then dipping the wrung leather in a mineral spirits solution of an alkyl or alkenyl succinic acid. This method has several disadvantages. In the first place the water content is a critical and important factor. Secondly this process must be effected as a dipping process. Attempts to apply the von Fuchs process to lubrication of leather in a drum were to no avail. A thick gelatinous mass was'formed that remained on the surface of the leather or clung to the surfaces of the drum. Little penetration of the ASA into the fiber resulted, and no lubrication was effected. The ASA remained completely in the aqueous gelatinous mass.

We have discovered how toprepare an aqueous emulsion of ASA, either alone or in the presence of other oils, that can be incorporated into chrome leather in conventional equipment as used in a conventional fat-liquoring process. The aqueous emulsion was achieved by including in the mixture a water-soluble, polar organic compound or mixtures of such compounds. Only a minor amount of water-soluble compound is needed, less than 25 percent of the amount of water taken as dispersing medium. Dispersions can be made of liquid or solid ASA and ASAs containing sixteen or more carbon atoms in the substituted alkyl or alkenyl succinic acid.

In a preferred embodiment of the invention, leather is lubricated by a process comprising impregnating unlubricated wet leather with an aqueous emulsion consisting essentially of about from 5 to 25 percent, based on wet drained weight of the leather of a relatively nonvolatile, water-soluble, polar organic compound or mixtures thereof and from about 0.25 to 2.0 percent ASA, based on wet drained weight of the leather, in sufficient water to provide an adequate float for distributing the emulsion throughout the leather.

It has been found that in the emulsified state the ASA emulsion is rapidly and efficiently absorbed by the leather and the process can be effectively carried out in a drum. No emulsifying agents such as soaps, sulfated oils, etc., need be added. Moreover, by the process of the instant invention, raw oils can be used with the ASA to give emulsions that can be satisfactorily used for fat-liquoring leather. The amount of ASA and- /or oil are not critical. We prefer to use about 1 percent of ASA and/or 5 percent of raw vegetable or animal oil; however, lesser or greater amounts of these may be used depending on the type of leather desired.

It has also been found that although the watersoluble, polar organic compound is an important factor in the preparation of the emulsion in which ASA and other oils are incorporated, it is not part of the actual lubrication process of this invention.

In addition to the fact that the process of this invention can be carried out in conventional fat-liquoring process equipment, a very important facet of the invention is that the emulsion is completely exhausted of the ASA or ASA plus other oils while the water-soluble polar organic compound remains behind in the float. Thus, the amount of oil that one desires to incorporate into the leather can be easily controlled merely by putting the desired amount into the emulsion.

The fact that the emulsion is completely exhausted of ASA or ASA plus other oils and that no measurable amount of the water-soluble polar organic compound is deposited in the leather was demonstrated by reextracting the fat out of the leather. ln all cases, regardless of the amount or combination of oils used the reextracted fat equaled that used in the emulsion showing that all the ASA or ASA plus other oils and only the ASA or ASA plus other oils is being removed from the emulsion.

Although typically applied to the leather in a volume representing a 50 percent float, larger or smaller volumes of emulsion may be used. Since the emulsions persist with widely varying dilutions in water, the important feature for efficient lubrication of the leather is that the ASA be dispersed in sufficient water to provide an adequate float for uniform distribution of the emulsion throughout the unlubricated leather.

No special treatment need be given to the tanned stock to prepare it for the lubrication process of the present invention. Chrome-tanned leather in the'blue (after neutralization to set the chrome tan) can be used directly without adjusting the pH of the stock. The lubrication process can be applied to any mineral-tanned stock such as chrome, alum, or zirconium tanned hides or skins. Likewise it may be applied to stock tanned with organic tanning agents such as vegetable tannins, aldehydes, epoxides, isocyanates, etc., or to hides and skins tanned with a combination of mineral and organic tanning agents. Especially preferable in our process is chrome-tanned leather. This may be used after neutralization of the chrome tannage as mentioned above, or if preferred, it-can be processed further such as retanned with vegetable tannins, glutaraldehyde, etc., or it may be colored prior to application of our lubrication process.

The water content of the stock is not critical in our process. The tanned stock may vary from a comparatively dry stock (i.e.,-wrung) to one that is soaking wet. We prefer to operate our invention at a somewhat elevated temperature, preferably about 40-55C., although temperatures below 40C. or higher than 55C. may be employed In the temperature range of 40-55C. the emulsion is exhausted in less than one hour.

Various water-soluble, polar organic compounds can be used as dispersants in this invention. Volatile solvents of this class such as acetone, isopropyl alcohol, methanol and ethanol serve to function as dispersing agents for the ASA and permit complete exhaustion of the ASA. The leather is, however, stiff, and these solvents are not preferred for the purposes of this invention.

Preferred compounds are the relatively less volatile water-soluble polar substances such as alkylene glycols and their ether and/or ester derivatives, polyalkylene glycols and their ether and/or ester derivatives, and ether and keto alcohols. These include tetrahydrofurfuryl alcohol, diacetone alcohol, ethylene and polyethylene glycols, propylene and polypropylene glycols, polypropylene glycol methyl ethers, glycol and polyalkylene glycol monoethers, glycol and polyalkylene glycol diethers, and glycol and polyalkylene glycol monoether monoesters.

Specific compounds operative in the invention include the glycols: dipropylene glycol, tetraethylene glycol, Carbowax 300, Carbowax 400, Carbowax 550, and hexylene glycol. Also included are the ether alcohols: diethylene glycol monomethyl ether (methyl Carbitol), diethylene glycol monoethyl ether (Carbitol), diethylene glycol monobutyl ether (butyl Carbitol), ethoxy triglycol, methoxytriglycol, and tetrahydro-furfuryl alcohol. Ethers and esters include diethylene glycol diethyl ether, cellosolve acetate, Carbitol acetate and dipropylene glycol methyl ethers. Also operative in the invention is diacetone alcohol. In the practice of our invention a minor proportion, relative to water, of the water-soluble polar organic compound is used. Any of the well-known methods for producing emulsions may be used. A convenient practice is to dissolve the ASA in the water-soluble polar solvent and then add the water with stirring. One may add raw vegetable or animal oil to the ASA if one so desires.

Practice of some preferred embodiments of the invention are demonstrated in Examples 1-5, 7-8, and 13-26, but are not intended to be in limitation of the scope of the invention. Example 6 serves to illustrate the critical significance of ASA in the leather lubricating systems. Examples 9 to 12 are included to illustrate the results obtained with volatile, low molecular weight, polar organic solvents.

EXAMPLE 1 Specimens of commercial chrome-tanned grain split leather in the blue were fat-liquored with emulsions consisting of one-fourth, one-half, 1 or 2 percent of alkenyl succinic acid (ASA), 5 percent tetrahydrofurfuryl alcohol (THFA) based on the drained weight of the leather and sufficient water to give a 50 percent float. The emulsion was prepared by warming the ASA in the tetrahydrofurfuryl alcohol and dissolving to a clear solution. The required amount of water at 50C. was added with stirring to'the solvent mixture whereupon an emulsion was formed. Fatliquoring of the wrung leather was carried out in the conventional manner maintaining the temperature of the fatliquoring system at 50 C. Complete exhaustion of the fatliquor was obtained in each instance in less than one hour. No adjustment of the system such as addition of acetic acid or salt to break the emulsion was required to reach complete exhaustion of the emulsion.

EXAMPLE 2 The procedure of Example 1 was followed with the exception that the tetrahydrofurfuryl alcohol was raised to 10 percent based on the drained blue weight of the stock. Complete exhaustion of the fat liquor was obtained in less than one hour.

EXAMPLE 3 The procedure of Example 1 was followed with the exception that the tetrahydrofurfuryl alcohol was raised to 15 percent based on the drained blue weight of the leather. Complete exhaustion of the fat liquor was obtained in less than one hour.

EXAMPLE 4 The procedure of Example 1 was followed with the exception that the tetrahydrofurfuryl alcohol was raised to 25 percent based on thedrained weight of the leather. Complete exhaustion of the fat liquor was attained in less than one hour.

EXAMPLE 5 The specimen of chrome-tanned grain split leather was retanned with 5 or percent glutaraldehyde (25 percent solution) as described by recommended procedures. The retanned leather was fatliquored in accordance with Examples 1-4 where one-fourth, one-half, l and 2 percent of ASA and 5, l0, l5 and 25 percent tetrahydrofurfuryl alcohol were used, respectively,

based on the drained weight of the leather. Emulsions thus formed with water were easily exhausted in less than one hour resulting in leathers that were flexible and soft, even softer than the chrome grain splits, (Example 4) which were not retanned. This shows that the invention is operative with various tannages.

EXAMPLE 6 additional hour. No emulsion was formed and little fatliquoring was attained by this system since globules of oil were visible on the walls of the jar and on the grain of the leather. Similar results were obtained even when the neatsfoot oil content was increased up to 6 percent and the THFA increased to percent based on the wrung blue weight. Thus it is clear that in the absence of ASA fat-liquoring or absorption of oil was not attained.

EXA PLE 7 The procedure of Example 6 was repeated except for the fact that 0.5 percent (based on the blue weight) of Casyl 18, an alkenyl succinic acid containing on the average a total of 22 carbon atoms (R IS in above general formula), was also added to the neatsfoot oil when dissolved in the THFA. A very nice emulsion was formed when water at 50C. was added to the solution of ASA and neatsfoot oil in THFA. Chrome-tanned stock warmed to 50C. was added and churned while maintaining the temperature at 50C. for one hour. Complete exhaustion of the fat liquor was attained as evidenced by clearing of the emulsion. Evidence as to complete exhaustion was also demonstrated by extracting the dried leather with chloroform. Extracted fat was equivalent to the total fat used in fat-liquoring the wet leather. Substantially similar results were obtained with higher or lower amounts of ASA, higher amounts of THFA and/or different types or amounts of raw oils, such as safflower, cod, soybean, and castor oil.

This compared to Example 6 shows the need for ASA to produce emulsions with raw oil useful for fatliquoring.

EXAMPLE 8 The procedure for Example 7 was followed with the exception that the chrome stock in the blue was retanned with glutaraldehyde before fat-liquoring. As in Example 7 the fat liquor was completely exhausted, and a mellow leather resulted.

EXAMPLE 9 A sample of a chrome grain split leather retanned with 10 percent glutaraldehyde (25 percent solution) was fat-liquored with 1 percent alkenyl succinic acid (ASA) dissolved with slight heating in 10 percent acetone (all percentages based on the wet wrung weight of the leather). The required amount of water, 40 percent based on the wrung weight, heated to C., was added to the ASA-solvent system and stirred. In this case a lightv emulsion was formed. The warm wet wrung leather was placed in the fat-liquoring system and churned for one hour under heat at approximately 50C. Exhaustion of the fat liquor was attained in one hour with temperature of the exhausted system at approximately 4042C. Leather fat-liquored with this system dried out rather stiff.

EXAMPLES 10-12 The procedure of Example .9 was followed with the exception that 10 percent (based on the blue weight) of. methanol (Example 10), ethanol (Example 11) and isopropyl alcohol (Example 12) were used in the separate examples in place of the 10 percent acetone. The dried leathers in the crust were stiff. These examples show that volatile organic solvents such as acetone, methanol, and isopropyl alcohol are not effective to produce the desired flexible, mellow lubricated leathers.

EXAMPLES 13-26 Y polyethylene glycol (Carbowax 400) (Example 18), di-

propylene glycol (Example 19), tetraethylene glycol (Example 20), hexylene glycol (Example 21), ethoxytriglycol (Example 22), propylene glycol monomethyl ether (Example 23), dipropylene glycol methyl ether (Example 24), tripropylene glycol methyl ether (Example 25), and diacetone alcohol (Example 26). The unstaked dried leather;i.e., the leather in the crust, from each of the above examples was flexible and mellow, comparable to crust leather after it has been mechanically staked.

Combinations of two or more of the relativelynonvolatile, water soluble, polar organic compounds have also been 'used, particularly combinations in which one of the solvents is tetrahydrofurfuryl alcohol and/or diethylene glycol monobutyl ether, to give flexible, mellow lubricated leather.

We claim:

1. A process for lubricating leather comprising the following steps:

a. lmpregnating wet leather by drumming it in conventional fat-liquoring equipment with a dilute aqueous emulsion consisting essentially of a relatively non-volatile, water-soluble, polar organic compound and mixtures of said compounds selected from the group consisting of diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, the acetate of diethylene glycol monoethyl ether, polyethylene glycol, dipropylene glycol, tetraethylene glycol, hexylene glycol, ethoxytriglycol, propylene glycol monomethyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, tetrahydrofurfuryl alcohol, diacetone alcohol and a compound of the formula RCH(CH CO H)CO H wherein R is selected from the group consisting of long carbon chain alkyl radicals and long carbon chain alkenyl radicals of from 12 to an average of 18 carbon atoms, dispersed in sufficient water to provide an adequate float for said wet leather, said impregnation being such that all of the latter compound is exhausted from the emulsion and incorporated into the leather and all but an immeasurable amount of the non-volatile, water-soluble, polar organic compound remains in the float;

b. removing the impregnated leather from the drumming equipment; and

c. staking and finishing said impregnated leather.

2. The process of claim 1 in which the water-soluble, polar organic compound is diethylene glycol monobutyl ether.

3. The process of claim 1 in which the water-soluble, polar organic compound is tetrahydrofurfuryl alcohol.

4. The process of claim 1 in which the water-soluble, polar organic compound is diacetone alcohol.

5. The process of claim 1 in which the watersoluble, polar organic compound is polyethylene glycol.

6. The process of claim 11 in which the watersoluble, polar organic compound is tripropylene glycol methyl ether.

7. A process for lubricating leather comprising the following steps:

a. Impregnating wet leather by drumming it in conventional fat-liquoring equipment with an aqueous emulsion consisting essentially of about from 5 to 25 percent, based on wet drained weight of said wet leather of a relatively non-volatile, watersoluble, polar organic compound and mixtures of said compounds selected from the group consisting of diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, the acetate of diethylene glycol monoethyl ether, polyethylene glycol, dipropylene glycol, tetraethylene glycol, hexylene glycol, ethoxytriglycol, propylene glycol monomethyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, tetrahydrofurfuryl alcohol, diacetone alcohol, and from about 0.25 to 2.0 percent, based on wet drained weight of wet leather of a compound of the formula RCH(CH CO H)CO H wherein R is selected from the group consisting of long carbon chain alkyl radicals and long carbon chain alkenyl radicals of from 12 to an average of 18 carbon atoms, dispersed in sufficient water to provide an adequate float for said wet leather, said impregnation being such that all of the latter compound is exhausted from the emulsion and incorporated into the leather and all but an immeasurable amount of the nonvolatile, water-soluble, polar organic compound remains in the float;

b. removing the impregnated leather from the drumming equipment; and 

2. The process of claim 1 in which the water-soluble, polar organic compound is diethylene glycol monobutyl ether.
 3. The process of claim 1 in which the water-soluble, polar organic compound is tetrahydrofurfuryl alcohol.
 4. The process of claim 1 in which the water-soluble, polar organic compound is diacetone alcohol.
 5. The process of claim 1 in which the water-soluble, polar organic compound is polyethylene glycol.
 6. The process of claim 11 in which the water-soluble, polar organic compound is tripropylene glycol methyl ether.
 7. A process for lubricating leather comprising the following steps: a. Impregnating wet leather by drumming it in conventional fat-liquoring equipment with an aqueous emulsion consisting essentially of about from 5 to 25 percent, based on wet drained weight of said wet leather of a relatively non-volatile, water-soluble, polar organic compound and mixtures of said compounds selected from the group consisting of diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, the acetate of diethylene glycol monoethyl ether, polyethylene glycol, dipropylene glycol, tetraethylene glycol, hexylene glycol, ethoxytriglycol, propylene glycol monomethyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, tetrahydrofurfuryl alcOhol, diacetone alcohol, and from about 0.25 to 2.0 percent, based on wet drained weight of wet leather of a compound of the formula RCH(CH2CO2H)CO2H wherein R is selected from the group consisting of long carbon chain alkyl radicals and long carbon chain alkenyl radicals of from 12 to an average of 18 carbon atoms, dispersed in sufficient water to provide an adequate float for said wet leather, said impregnation being such that all of the latter compound is exhausted from the emulsion and incorporated into the leather and all but an immeasurable amount of the nonvolatile, water-soluble, polar organic compound remains in the float; b. removing the impregnated leather from the drumming equipment; and c. staking and finishing said impregnated leather. 